The team, whose findings appeared in Nature, solved the puzzle of how the hormone insulin binds to its receptor in cells - a process necessary for cells to take up sugar from the blood and essential for treating diabetes.

"All of that (previous) work has taken place without a detailed picture of how insulin actually interacts with the cell and tells that cell to take up glucose from the blood," leading scientist Mike Lawrence, at Australia's Walter and Eliza Hall Institute in Melbourne, told Reuters.

"What we've done is providing that picture," he said of the three-dimensional view of insulin bound to its receptor that appeared in Nature on Thursday.

Researchers found that insulin engages its receptor in a very unusual way, with both insulin and its receptor rearranging themselves as they interact.

"A piece of insulin folds out and key pieces within the receptor move to engage the insulin hormone," Lawrence said in a statement. "You might call it a 'molecular handshake'."

Insulin controls the levels of glucose, or sugar, in the blood, a mechanism that breaks down in people with diabetes.

Understanding the insulin binding process could lead to new ways to deliver insulin other than by injection, or the development of more effective and longer-lasting insulin products, Lawrence said.

"This structure is going to be a reference point for all future design of insulin," he said.

"They (drug makers) are going to use that information...for the next generation of insulin delivery devices, etc."

There are now 371 million people living with diabetes globally, up from 366 million a year ago, according to the latest report by the International Diabetes Federation.